Read the complete report here:
"A blockage in this artery is usually due to trauma, such as a broken arm or collar bone, though it can also be caused by the presence of an extra rib, called a cervical rib.
This abnormality is present from birth in one in 200 of us but, over time, it can press on the artery and cause damage, triggering a clot.
It is easily diagnosed on X-ray, and, if there are no symptoms, we leave it alone. But if the rib is causing pain by compressing vital nerves, or affecting the functioning of the arm by pressing on a blood vessel, then surgery may be essential."